A high-temperature superconductive material, which is known as a ceramic superconductor, is coated with a metal and strongly worked into a thin tape by deformation processing. It has been recognized possible to attain a high critical current density by combining such deformation processing with heat treatment.
In order to apply such a tape-shaped high-temperature superconducting wire to a coil, for example, it is necessary to wind the wire, generally around a bobbin. In particular, such a tape shaped high-temperature superconducting wire is properly wound into the form of a double pancake coil. In such a double pancake coil, a single high-temperature wire is adapted to form two coil portions. Therefore, a throughout portion extending from one coil portion to the other coil portion is required. In relation to employment of the tape-shaped high-temperature superconducting wire, however, it has been recognized that the critical current density is reduced due to shearing stress which is applied to the throughout portion, since the wire is necessarily twisted at the throughout portion.